THE CHARACTERIZATION AND IDENTIFICATION OF A NATURALLY-OCCURRING HYBRID IN THE GENUS LEUCAENA (LEGUMINOSAE, MIMOSOIDEAE)

Phytogeographical, morphological, and molecular evidence for the wides pread but sporadic occurrence of sterile hybrids between Leucaena leuc ocephala subsp. glabrata and L. esculenta subsp. esculenta in South-Ce ntral Mexico is presented. Most morphological and DNA characters studi ed in the putative hybrids showed states intermediate between the prop osed parental taxa. The occurrence of non-additive nuclear ribosomal D NA phenotypes is discussed and the need to use a suite of nuclear taxo n-specific markers to determine hybridity is emphasized. The origin of the hybrid is discussed in relation to the disruption of the distribu tions of both parental taxa through use by man as minor food plants, p roviding another example of the important influence of human interfere nce on the evolution of Leucaena. The successful use of dried leaf mat erial as a source of DNA is highlighted as an efficient way to identif y sterile hybrids at the molecular level.